A person who's a very obnoxious asshole. An anal flagger is someone who has passed the level of douchebag in their behavior and is headed for asshat status.
Steve: "Everyone hates Todd because he's so rude and obnoxious! He acts like such a douchebag!"
Ryan: "Yeah, Todd's a real anal flagger!"
Code between jamming buddies to use the Flanger effect pedal on the guitar for the song they're about to play.
A warm hearted reference to Ned Flanders, neighbor of The Simpsons.
A person who claims to be in a gang but is not an offical member. The only thing that makes them a member is the fact that no one else around him/her knows the truth.
Guy1: Wut up folks?
Guy2: Shit nigga(shakes up and walks off)
Guy3: (to Guy1)Dont do that shit again. He aint folks he a false flagger.